"The 12 inch ball shall have a core wound with a fine quality twisted yarn to 11 5/8 to 11 3/4 inches in circumference. The completed ball shall be 11 7/8 to 121/8 inches in circumference, and shall weigh between 6 and 7 1/4 ounces."

0.170–0.206 kg(12-inch ball)

"The completed 11 inch ball shall be between 10 7/8 to 11 1/8 inches in circumference and shall weigh between 5 7/8 and 6 1/8 ounces."

0.167–0.174 kg(11-inch ball)

Softball is a modified version of baseball. There are only
a few differences between the two sports. The rules, the pitch
speed, the field, and the equipment are the only differences.
There are three variations of softball, slow-pitch, fast-pitch,
and modified-pitch. The equipment is only slightly different based
on their specifications. The difference found in the field is
its size. The softball field is smaller than a baseball field.

The pitches for these different variations are all underhand. The speeds of
the tossed ball goes as the name says. In slow-pitch, there's a height requirement
that must be met for the highest position of the ball. It must remain between
6 and 12 feet (1.83 m and 3.66 m) above the ground. For Modified-pitch, there
aren't any flight path requirements, but there are requirements for the way the
ball is tossed.

The ball used, is slightly larger than a baseball and slightly
heavier. It must be thrown underhand, as stated previously. There
are a few balls that are used in softball depending on the choice
of the teams. Measurements for these balls are based on the circumference
around the ball. The 11-inch ball (0.28 m) is used in women's
softball. The 12-inch (0.31 m) ball is the standard issue ball.
The 16-inch (0.41 m) ball is used frequently for softball games
in Chicago.

This sport was created as an indoor sport in Chicago. It was
later modified to an outdoor sport to keep firemen up to par with
the name Kitten League Ball or Mush Ball. It later gained national
recognition and had its name changed to diamond ball. Afterwards,
it was changed to softball. The International Softball Federation
was created as the sport gained international recognition. In
1996, a Women's Softball Competition was added to the Olympics.